I was just wondering if i could get Just Cause 2 on my mac book air, and if i could 1. how good are the graphics, and 2. would i be able to get the multiplayer mod cause if i try to get it it says it only works on a windows computer

Well, the game was never made for Mac so you're out of luck, unless you want to create a Bootcamp partition or use something like Parallels.

If you did have a way of running Windows games, how good they would be would depend on how old your MBA was, specifically the graphics card. Intel cards are traditionally pretty underpowered, but they can run some games ok. The main problem with an Air is that the processor is pretty weak, but the SSD usually helps make up for it a bit.

i bootcamp through my 2011 imac. Only 2 changes have been mad from stock: replaced the HDD with an SSD and have upgraded to 16gb ram. It all depends on your graphics card. I think it would be tough on and MBA, but not on an MBP.